Mowabusa, has claimed the Guinness record for the world's fastest lawnmower with a vehicle built at home by a retired air conditioner engineer

 

powered by the 1,300cc engine from a Suzuki Hayabusa superbike and also uses the front suspension from a car and a trike conversion kit in the rear, and it was clocked at an average speed of 143 mph to break the previous mark of 133 mph, at the Elvington Airfield in York, U.K.

it took 2 years of work, and about 30k British pounds

https://www.thesun.co.uk/news/16337511/guinness-world-record-fastest-lawnmower/